Page 161 - Engineering Plastics Handbook

134 Engineering Plastics

Methanol/
water
Vacuum
1,4 BG
DMT/
TPA EI
reactor
PC Vacuum
reactor

1,4 BG/
catalysts Pelletizer

PBT
product
Figure 7.2 Schematic of a polybutylene terephthalate manufacturing
flowchart.

Transesterification
O
COCH 3 + HO — (CH 2 ) 4 — OH
O
CO — (CH 2 ) 4 — OH + CH 3 OH

Direct esterification
O
COH + HO — (CH 2 ) 4 — OH
O
CO — (CH 2 ) 4 — OH + H 2 O

Polycondensation
O
2 CO — (CH 2 ) 4 — OH

O O
CO — (CH 2 ) 4 — OC + HO — (CH 2 ) 4 — OH

Figure 7.3 Synthesis of PBT via esterification and polycondensation reactions.